Glass or ceramic-to-metal seals

ABSTRACT

Glass or ceramic-to-metal composites or seals wherein the glass or ceramic is bonded to a copper base alloy having a thin film of Al2O3 on its surface. The Al2O3 film comprises at least 10 percent, up to 100 percent, of the oxide film thickness on the metal. The copper base alloy preferably contains 2 to 10 percent aluminum with C.D.A. Alloy 638 being the most preferred alloy. The invention also includes the process of bonding the glasses or ceramics to the metal. Substantial mismatch between the coefficient of thermal expansion of the glasses or ceramics and the copper base alloys may be tolerated in accordance with this invention.

United States Patent 1191 Pryor et all. i 1 Apr. 10, 1973 v GLASS ORCERAIVHC-TO-NIETAL References Cited SEALS .UNITED STATES PATENTS [75]Inventors: Michael J. Pryor, Woodbridge; 3,351,700 11/1967 Savolainen eta1. ..174/50.56 James M. Popplewell, Guilford, both 3,546,363 12/1970Pryor etal ..174/525 ofConn. 3,618,203 1l/1971 Pryor 174/50.56X [73Assignee: 01111 Corporation, New Haven, Primary m n -B A-Gilheany Y ConnAttorney-Robert H. Bachman et a].

22 Filed: Feb. 17,1972 1 1 ABSTRACT 1 1 v Glass or ceramic-to-metalcomposites or seals wherein PP 2 1 y the glass or ceramic is bonded to acopper base alloy 1 1 having a thin film of A1 0 on its surface. The A10 Related Appuafion Data film comprises at least 10 percent, up to 100percent, I of the oxide film thickness on the metal. The copper baseallo referabl contains 2 to 10 ercent alu- 62 1) f8 .N 1. 78,899, OCL 7,1970, P 1. N Y P Y P y er 9 a o minum with C.D.A. Alloy 638 being themost I 1 preferred alloy.. The invention also includes the [52 11.8. C1..Q ..174/50.6l, 161/196 Process of bonding the glasses or ceramics tothe 51 1111. c1 ..H01j 5/00 metal Substantial mismatch between thecoefficient 5s .Fieldof sarcasm-1.2;"; ..l74/50.61, 50.63, of themalexpansion of the glasses of ceramics and the copper base alloys may betolerated in accordance with this invention.

. 9 Claims, 4 Drawing Figures 2 COP/DEE 5,455. /3

, 2% mzag ALL/M/Afl/M m 1. 01 co/vmwl/va 0A C EIP/QM/ C GLASS ORCERAMIC-TO-METAL SEALS This is a division, of application Ser. No.78,899,

filed Oct. 7, 1970, now U.S. Pat. No. 3,676,292.

There are many metal-glass-ceramic applications and systems which havein common the bonding of a glass or ceramic material to the surface of ametal. One common application is for making hermetic sealsfor it. The A1film comprises at least percent of the total oxide film thickness. Whena glass or ceramic is bonded to this copper base alloy having the M 0film, a strong bond results.

Because of the high bond strength between this 7 copper base alloy andthe glass or ceramic, it is possible metal cased semi-conductor devices.Characteristically, in the known glass or ce'ramic-to-metal seals, the

oxide on the metal acts as the bonding agent in that it is bonded to theunderlying metal and the glass or ceram- ,ic material. Therefore, thecharacteristics of the metal sess poor mechanical properties. Therefore,the prior art glass or ceramic-to-metal composites and seals, have beendesigned to minimize the stresses developed at the bond interfacebecause of its relatively poor strengthalt is generally known that thoseglasses and ceramics which possess the desirable bonding and sealingcharacteristics also have coefficients of thermal ex- Therefore, theprior art hasdeveloped a series of low to fabricate glass orceramic-to-metal composites or seals with a high degree of mismatch ofcoefficient of thermal expansion between the glass or ceramic and themetal. Therefore, the glass or ceramic-to-metal composites or seals inaccordance with this invention eliminate the necessity of using thecostly nickel containing low expansivity alloys and, further, they maybe fabricated without the oxidizing pretreatment usually employed withthe low expansivity alloys of the prior art. There is also a markedimprovement in electrical and thermal conductivity as compared to thelow expansivity alloys.

expansivity metal alloys, which have coefficients of thermal expansionfor a limited temperature range so -which reasonably closely match thecoefficients of a thermal expansion of many sealing glasses or ceramicsIt is accordingly an object of this invention to provide a glass orceramic-to-metal composite or seal having improved bond strength betweenthe glass or ceramic and the metal, and to provide a process of makingsame.

It is a further object of this invention to provide a glass orceramic-to-metal composite or seal wherein the metal is a copper basealloy, which forms a thin film of A1 0 on its surface.

.It is a further object of this invention to provide a glass-to-metalseal assembly for encasing semi-conductor devices wherein the metal is acopper base. alloy as set forth in Table I. I which forms a thin film ofA1 0 on its surface.

' TABLE I i Thermal expansion Material Composite coefi. in./in./ C.

l I 41Xl0 (at 20 C.). KovarASTM No. F-68 (Reason... Fe+29%Ni+17%-G0+0.45%Mn+0.10% Sl+0.02% c figg gig fi q 49X10 (range 0-400 C.).Nickel 100% N1. 128X10' (at 20 C.). Nlron 52 ASTM N0. F-30-6 517 Ni,49%Fe. 98X10- (range 500 0.). Niron 42 AS'IM NO. F-68.. 41 0 Ni, 59% F47X10' (range 30300 C.). Nlron 46 ASTM NO'. F-30-68. 46% Ni, 54% Fe.77X10' (range 30350 C.). Dumet ASTM N0. F-ZlJ-GS.-. 43% Ni, Fe 68 10(range 30400 C.). Sylvania No. 4 ASTM N0. F- 42% Ni, 6% Cr, 52% Fe s910- (range 30350 0.). Soda-lime-silica glass 70% S102, 11% CaO, 14%Na2O-l-Al2Oa+Mg0- 90 (10- (range 0100 0.). Porcelain (electricalgranulation) g oLeucite (K20, A110 4Si0g), 30% Mullite (3Al203, 2Si02),30%. 60x10 (range 0-1,000 0.). l 2.

Sealing glass type 101 ASTM N0. F-7967T. 56% S102, 1.5% A1203, 4.0% K20,29.0% PbO 92 (10' (range 30-300 C.).

Unfortunately, they range of low expansivityalloys which have beendeveloped are not otherwise particularly desirable materials. In thefirst place, they are characteristically quite costly. Further, sincealmost all are nickel based alloys or contain large proportions ofnickel, their thermaland electrical conductivity is very poor. Thecorrosion resistance of the majority of the low expansivity alloys isalso relatively poor. It is known that to obtain good glass adherenceparticularly to the bare low expansivity alloys, they usually requirepretreatment to form a relatively thick oxide film.

Further, the oxides formed, e.g., iron oxides, nickel ox- Other objectsand advantages will'become apparent to those skilled in the art as adetailed discussion of particular embodiments proceeds with reference tothe drawings which form a part hereof, in which:

FIG. 1 is a cross sectional view of a glass or ceramicto-metal seal inaccordance with this invention.

- FIG. 2 is a cross sectional view of a glass or ceramic- -to-metal sealassembly in accordance with this inventron FIG. 3 is a side view of atypical lap-type glass or ceramic-to-metal seal.

FIG. 4 is a cross section of a typical butt-type glass orceramic-to-metal seal.

In accordance with this invention, it has been found that copper basealloys with relatively higher thermal expansivities than the glasses orceramics can be used in glass or ceramic-to-metal composites or sealsprovided that the copper base alloy has certain inherent oxidationcharacteristics. The characteristics required in the copper alloy arethat it has formed on its surface copper base alloys for use in theglass or ceramic-tometal composites or seals of this invention containfrom 2 to 12 percent aluminum. Preferably, they conmin from 2 to percentaluminum, 0.001 to 3 percent" silicon and a grain refining elementselectedfrom the group consisting of ironup to 4.5 percent, chromium to1 percent, and mixtures of these grain refining elements. In particular,C.D.A. Alloy 638 containing 2.5 to 3.1 percent aluminum, 1.5 to 2.1percent silicon and 0.25 to 0.55 percent cobalt is most useful in theglass or ceramic-to-metal composites or seals of this invention.

- Impuritiesmay be present in amounts not adversely affecting theproperties of the glass or ce'ramic-to-metal composites o'rseals of thisinvention. In particular, the impurities may include less than 1 percentzinc; less than l percent nickel; less than I percent manganese;

- up to 1 percent, zirconium, up to 0.5 percent, cobalt up less than lpercent tin; less than 0.5 percent lead; less than 0.1 percentphosphorus; and less than 0.1% arsenic.

The alloys useful-vwith-this invention and especially Alloy 638 haveexcellent high temperature oxidation resistance due to the formation ofthe protective alumina filmL When the metal is oxidized in air, the alumina film isoverlain with a thinlayer of copper oxides.

Controlled oxidation in a wet reducing atmosphere prevents theformationof the copper oxides and, induces a film to form which issubstantially'completely alumina. Alumina seals efficiently to-mostglasses and ceramics. Therefore, since the alumina film formed on thealloys used with this invention istightly adherentto the alloys, anexcellent glass or ceramic-to-m'etal bond isproducedt v v Atypicalglass-to -metal seal according to the present invention is illustrated.in FIG. '1. As seen therein,

copper base alloys in accordance with this invention in I the form of asheet material have been drawn into a cup shaped header 1. The header 1comprises a base porbase region 10, and a collector region 11, isconventionally affixed to the base portion 2 of the header 1.

Three of the wires 5 are connected to the respective base 9, emitter 10and collector l1 portions.

A metal cap 12 is then snugly fit around the wall portion 3 of theheader 1 and resistance welded at, 13 to the header flange 4. The cap 12may be made of any appropriate metal or alloy, but it is preferred touse the copper base alloy used in the glass-to-metal seal. The

remaining wire 5 may be grounded to the metal'cap 12.

While the glasseto-metal sealing system has been.

shown as applied to the specific configuration of FIGS. 1 and 2, it isapplicable to any typeof package where a hermetic or-other type ofglass-to-metal seal is desired. As will be demonstrated hereinafter, theseal preferably should be designed suchthat the net residual stresses inthe glass after manufacture are compressive in nature rather thantensile in nature. The configuration of FIGS. land 2 is a typical designfor-a compressive type glass-to-metal seal. Because the metal headerseeks to shrink more upon cooling than the glass due to the differenceof 'coefficients of thermal expansion, the result:

"ing net residual stresses of the glass after the seal has beenfabricated are compressive'in nature.

In general, glasses or ceramics possess rather high strengths incompression and, therefore, are able towithstand high residualcompressive stresses. The metal itself isductile and in the event thatthe tensile stresses generated in the metal as it compresses the glassexceed its yield strength or tensile strength, it will yield reducingthe-net stresses.

. To demonstrate the effectiveness of the glass andceramic-to metalcomposites or seals of this invention a v series of experiments were runas follows.

I Materials Selected for Glass-Metal Sealing Three glasses were selectedto give a range of thermal expansion coefficients from 41 X 10" /C to117 X 10 /C. These glasses are all commercially available and are incurrent use for making glass-metal seals. The

tion 2 integrally connected to one end of a wall portion I t 3 and aflange. portion 4 integrally connected'to the other end of the wallportion 3. The header may be of any desired shapewith the wall portion 3being; circular, rectangular or anyother shape as required by thespecific application. 1

. The wires15 which may ,be made of the alloys in accordance with thisinvention pass through apertures 6 in the base portion 2 of theheader 1. After these wires 5 have been placed through the apertures 6,a glass or ceramic in powder form is placed into the header, melted, andthen allowed to solidify. By virtue of the sealing properties of .thecopper base alloys used with been inverted. A semi-conductor device 8,for example, a silicon transistor having an emitter region 9, a

propertiesfof the glasses are given in Table II together withtherelevant manufacturers information.

TABLE II Coefficient of Com- Sub- Expansion Sealing patible sequentGlass Type in/in/C Tempera- Material at- 7 ture ment ii s- 4l X10" 615CRodar None mois necessa 13 but ml! relieve if required fia 131i: 117 X10'' 365C Nickel None necessa 00583 but me relieve if i required G.E.ReX X 10- 500C. None Stated Recrystallization Alloy 638 was selected asexemplary of the alloys I film only) and in air (alumina overlain withcopper ox- Several different cooling methods were employed, ides).especially in seals where the difierences in expansion Seal Types 7coefficients between glass and metal were high. A slow In order togather the maximum amount of informaair cool was employed in many caseswhich involved tion, two types of seals were made and tested. These in-5 slowly withdrawing the metal from the heat source over eluded lap andwire butt seals. The lap seal 20 is illusabout 15 minutes. Hotplatecools were also used in an trated in FIG. 3 and comprises two strips ofmetal 21 attempt to stress relieve the joint at an intermediate with aglass or ceramic 22 sandwiched between the temperature before cooling toambient. The hotplate overlapped surfaces. This arrangement hasglass-towas at a temperature of about 150C and after sealing metal bondsat interfaces 23 and 24. The butt-type seal glass and metal, the jointwas held at this temperature 30 is illustrated in FIG. 4 and comprisestwo metal for minuteswires 31 which are aligned along their longitudinalaxes Each Of e glasses us d so Cou d be gi en some and bondedtogether bya mass of glass or ceramic 32 kind of a heat treatment subsequent tomaking a seal in v i glass to-metal bonds fo ming at i terfa s 33 d 15order to partially stress relieve or recrystallize the glass. .34. Thesetreatments were carried out according to manup joints were used so h agood indication'of h facturer's recommendations and are described below.relativezwettabilities of the various glasses on the metal could beobtained by estimating visually the contact Package Sealant 00583 anglebetween the glass and metal. Wettabilities can e finished seal washeated for 30 minutes t vary from poor (high contact angle with poor fl365C. This treatment ensured good reheat properties characteristics) toexcellent (low contact angle with fi u good flow characteristics). Ingeneral, it would be exhalf inch and one-fourth inch wide was used inmaking lap seals. The two different strip widths were comparedPackage-Sealant 00130 pected that the seal strength would increase asthe bili i d; i The finished seal was heated at 615C for 45 The wirebutttype seal can be considered to be more nfinutes- 3 treatment ensuredgood reheat P p truly representative of an encapsulationseal where the ito 5 50 metal leads are enclosed in the glass. Very little informationconcerning wettability can be obtained with this type of seal. However,differences in thermal expansion HTheIeCTYSIamZaUQn for the GeneralEleccoefficient can Show as significant differences in trrc ReX Glasswas carried out as follows: The glass was fracture stress values; iheated at 590 C and held for two hours. The temperap Seals ture was thenraised over two hours to 830C and held I for four hours. The temperaturewas then dropped to Strip material of about .030 inch gauge at both onevambient at per hour This treatment produced a milky white glass whichwas completely recrystallized and had the desired electrical properties.Butt in order to determine whether the effect of differences Seals;

in expansion coefficient would be less marked in the Th b tt s al wasmade by aligning two straight General Electric ReX Glass narrower seals.After the appropriate metal preheatpieces of wire together andsurrounding the ends of the treatment the glass of interest was heatedin air in conir with a lass bead as shown in FIG. 4; Particular tactwith the metal. The glass was applied over about care was taken,however, to ensure good alignment of one-half inch of the end of eachhalf of the lap as a finethe wires. The fracture strength of these sealswere I 1y divided powder. After the glass'had becomefluid and measuredin a similar manner to those measured for lap has wet the surfaeejof themetal, the ends of the lap l I were aligned, pressed together and thejoint allowed to The fracture stresses and wettabilities are given incool. Tables III through V.

' TABLE matron EXPANSION PACKAGE SEALANT 0583 Expansion Coefficient 11710- in./in.l C.

Expan.

. coeft. in./ Type Fracture I Subsequent Description in./ C. of sealCooling stress, p.s.i. Where fracture Wetting heat treat Alloy 638Asrecdsheetnn. 220 Glass" Excellent None.

0 do 0.. Do. 40 A film sheet 625 do. Do. 250 .do Do. 370 .do.. d Do."do"... Furnace..." 180 .do. .do 30 mins. 365 C.

Nora-Difference in thermal expansion coefiicient between alloy 638 andglass 53X10- in./in./ C.

Thain IVAREX GLASS Expansion Coefiioient 90x10- in./in./ C.

Expan. I Coeif. in./ Type of Fracture Subsequent Description in./"- 0.seal 7 Cooling stress,p.s.i. Where fracture Wetting heat treat Alloy 638As-rec'd sheet Do. 0 D Abraded sheet 0 D0 0 Pre-oxidized sheet in fia 040 A. film.-. 0 I Do 0 200 A. film p 0 Do. Lap... 0 Wire as-recd...Butt- 300 Do .do 170 Glass Do. Do. .do. 122 do. .1 Do. Do... do F 264do.. do Recrystallized. Abraded wire .do. Slow air... 320 InterfaceExcellent None.

Do .tlo... Air. 170 lass. Good Do. Pro-oxidized wire in flame .do Slowair. 270 Interface and glass Excellent Do.

Norm-Difference in thermal expansion coefficient between alloy 638 andglass 80X10- in./in./ 0

TABLE V.-LOW EXPANSION PACKAGE SEALANT 00130 Expansion Coclllclcnt 41x10in./in;/ C.

Expan. coetf. in./ Type of Fracture Subsequent Description in./ C. sealCooling stress, p.s.i. Where fracture Wetting heat treat Alloy 638 170x10- As-recd sheet and all treatments Lap Air 0 Interface and glass.Exeellent None. As-recd wire and all treatments Butt. Air 0 InterfaceFair o.

Norm-Difference in thermal expansion coefficient between alloy 638 andglass 129 10- in./in.l C.

The: fracture stress values (average of three specimens) quoted in psihave been corrected for-area.

Past experience has shown that glass-metal seal frac-- ture stresses arein general not very reproducible, especially since the majority of goodseals fail in the glass and many of these at lowv stress values. This iseasily un-' derstood on the grounds that if significant contractionstresses, are induced in the glass on cooling, very little additionalexternal load will be required in order to ex-.

ceed the tensile strength of the glass. The internal stresses presentinv glasses-are invariably anisotropic in nature especially in amorphousglasses." The stress anisotropy considerably affects the resultanttensile strength of the glass. Seals that fail in the glass would,therefore, be expected to have variable fracture stress are highlysensitive to thermal expansion coefficient values. It is not possible ina glass-to-metal seal to completely stress relieve the joint even if theexpansion coefficients of metal and glass are closely matched.Therefore, none of the fracture stress values quotedin Tables lIIthrough V are absolute bond strengths nor can they be'related toabsolute bond strengths. They are, however, representative of actualseal strengths made under the stated specific conditions- 1 Nosignificant differences in fracture stress were observed betweenone-fourth inch and one-half inch wide specimens indicating that thegeometry of the sample is unimportant to this type of seal.

The lap joint was found to be extremely susceptibleto thermal stressesduring cooling when I large differences in thermal expansion coefficientare involved. Seals-that fractured in the glass indicated that thetensile strength of the glass was less thanthe glass-metal bondstrength.

- The results indicate several trends. The difference in thermalexpansion coefficient between the glass and metal appears to be ofsignificant importance. I Moreover, wettability appears to be 'anecessary factor in making a successful seal.

in most seals made the glass wet the metal extremely well. Anycopperoxides formed in making the seal dismismatch. The fracture stress valuesindicate that a good lap seal can be made with Alloy 638 provided thatstresses developed during seal fabrication are not sufficient to causefailure in the glass.

The sensitivity of glass-Alloy 638 lap seals to thermal expansioncoefficient mismatch is easily explainablc sincein all systemsinvestigated, the metal had a much high expansion coefficient than theglass and net tensile stresses developed on cooling. However, since theoxide layer is extremely thin and tightly adherent to the metal, failurealmost always occurs in the glass and not in the oxide layer at theglass-metal interface. Therefore, it is evident that Alloy 638 forms astrong bond withthe glasses investigated, and failure of the seal is dueto failure of the glass and not the bond.

As previously mentioned, surfacetreatment did not significantly affectthe bond provided the metal was free from organic material.

. Butt seals could be made successfully between Alloy 638 and the higherexpansivity glasses. it is evident from Tables Ill through V that buttseals made with Alloy 638 are less sensitive to thermal expansioncoefficient mismatch. The seals can tolerate a great degree of mismatch.At any particular mismatch value,'the fracture stress of a glass-Alloy638 butt seal is much higher than for the lap seal. This is because thestresses developed in the glass on making a butt seal with Alloy 638 aremainly compressive whereas they are mainly tensile in the lap seal.

Alloy 638 seals were'found to be insensitive to subsequent stress reliefor recrystallization treatment; very I little difference in fracturestress values being observed in most cases.

The data in Tables Ill through V clearly demonstrate that Alloy 638which is typical of the alloys useful in the glass-to-metal seals ofthis invention bonds strongly to all of the glasses investigated. Inevery case, the strength of the glass-to-metal bond was stronger thantensile strength of the glass..lt has also been shown that theglass-to-metal seals in accordance'with this invention can tolerate ahigh degree of thermal expansion coefficient mismatch without failureespecially if the details of operation. The invention rather is intendedto encompass all such modifications which are within its spirit andscope as defined by the claims.

What is claimed is: 1. In a glass or ceramic-to-metal seal comprising acup shaped metal header, said header having a base resulting netresidual stresses in the glass arecompressive in nature. However, if thenet residual stresses in the glass are tensile in nature, the amount ofmismatch tolerance is determined by the glass.

' It has been found that where the net residual stresses "in the glassare tensile in nature, the mismatch in thermal expansion coefficientbetween the metal and glass should preferably be less than 75 X10in./in./C and still more preferably, be less than 60 X 10- in./in./C.However, greater degrees of mismatch can be tolerated with'strongerglasses. It has been found that where the net residual stresses in'glass'are compressive-in nature, the mismatch in thermal expansioncoefficient between the metal and glass can be as high as 110' X10--in./in./ C though preferably," it should be no greater than 80 X 10"in./in./C. However, even greater degrees of mismatch can be tolerated ifstronger glasses are employed.

The data in Tables III through V also establish that the wettability ofthe alloys used in the seals of this invention is usually excellentprovided the surface is free from organic contaminents. Further, thegl'ass-to-metal seals in accordance with this invention are insensitiveto subsequent heat treatment and, therefore, glasses requiring stressrelief or recrystallization canbe used.

tensile strength of the portion with a plurality of apertures therein, awall por-. tion integrally connected to said base portion and a angeportion integrally connected to said wall portion;

a plurality of metal wires extending through said apertures in said baseportion of said header; a glass or ceramic at least partially fillingthe cup shaped header and being hermetically bonded to said wires and tosaid header, the improvement wherein said metal header is a copper basealloy containing 2 to 10 percent aluminum and the balance essentiallycopper.

2. In a glass or ceramic-to-metal seal as in claim 1,

' the further improvement wherein the copper base alloy to 2.1 percentsilicon, 0.25 to 0.55 percent cobalt, and

' the balance essentially copper.

4. In a glass or ceramic-to-metal seal as in claim 3,

' the further improvement wherein theresidual stresses in said glass orceramic are compressive in nature and whereinthe mismatch in coefficientof thermal expansion'between the glass or ceramic and the copper baseTests similarto those described above for Alloy 638 "glass-to-metal'seals, when carried out using plain copper which had not been borated,did not yield viahis seals.'ln general, the glasses did not wet coppervery well and did not bond well'to the copper. Any bonds which. were,obtained appeared to be mechanicalin nature and all fractures occurredat the gIlass-to-metal interface.

I In summary then, in accordance with the instant invention, a group ofspecific copper base alloys has been found to yield glass-to-metal sealshaving markedly improved bond strengths-between the glass and the metal.The metal has substantially higher thermal and electrical conductivitiesand is less expensive than the materij als commonly used by theprior'art. It is certainly surprising that glass-to-metal seals can befabricated in accordance with this invention wherein there is a substantial mismatch between the glass or-- ceramic and the copper and normallya borating step is required to form any type-of a seal. In accordancewith this invention a borating stepis not employed. I

It is to be understood that the invention is not limited to theillustrations described and shown herein, which are deemed to be-merelyillustrative of the best modes of carrying out the invention, and-whichare suitable of alloy is less than 1 10 X 10 in./in./C.

5. In a glass or'ceramic-to-metal seal as in claim 3, the furtherimprovement wherein both said metal header and said metal wire areformedof an alloy containing 2 to 10 percent aluminum, thebalance essen-'tially copper.

6. In a glass or vceramic-to-metal seal as in claims, the furtherimprovement wherein the copper base alloy comprises 2 to 10 percentaluminum, 0.00l to 3 percent silicon and a grain refining elementselected from the group consisting of iron up to 4.5 percent, chromiumup to l'percent, zirconium up to 0.5 percent, cobalt up to 1 percent andmixtures thereof, and the balance essentially copper.

7. In a glass or ceramic-to-metal seal as in claim 6, the furtherimprovement wherein the copper base alloy consists essentially of 2.5 to3.1 percent aluminum, 1.5

I. metal. This is especiallythe case since it is known in the art thatthe glasses or ceramics do not seal well to plain to 2.1 percentsilicon, 0.25 to 0.55percent cobalt and the balance essentially copper.

8. In a glass or ceramic-to-metal seal as in claim 7, the furtherimprovement wherein a semi-conductor device is secured to the baseportion of said metal header and a metal cap is placed over said metalheader so as to enclose the semi-conductor.

modification of form, size, arrangement of parts and 9. In a glass orceramic-to-metal seal as in claim 8, the furtherimprovement whereinresidual stresses in said glass or ceramic are compressive in nature andwherein the mismatch in coefficient of thermal expansion between theglass or ceramic and the copper base alloy is less than 1 10 X 10"in./in./C.

2. In a glass or ceramic-to-metal seal as in claim 1, the furtherimprovement wherein the copper base alloy comprises 2 to 10 percentaluminum, 0.001 to 3 percent silicon and a grain refining elementselected from the group consisting of iron up to 4.5 percent, chromiumup to 1 percent, zirconium up to 0.5 percent, cobalt up to 1 percent andmixtures thereof, and the balance essentially copper.
 3. In a glass orceramic-to-metal seal as in claim 2, the further improvement wherein thecopper base alloy consists essentially of 2.5 to 3.1 percent aluminum,1.5 to 2.1 percent silicon, 0.25 to 0.55 percent cobalt, and the balanceessentially copper.
 4. In a glass or ceramic-to-metal seal as in claim3, the further improvement wherein the residual stresses in said glassor ceramic are compressive in nature and wherein the mismatch incoefficient of thermal expansion between the glass or ceramic and thecopper base alloy is less than 110 X 10 7 in./in./*C.
 5. In a glass orceramic-to-metal seal as in claim 3, the further improvement whereinboth said metal header and said metal wire are formed of an alloycontaining 2 to 10 percent aluminum, the balance essentially copper. 6.In a glass or ceramic-to-metal seal as in claim 5, the furtherimprovement wherein the copper base alloy comprises 2 to 10 percentaluminum, 0.001 to 3 percent silicon and a grain refining elementselected from the group consisting of iron up to 4.5 percent, chromiumup to 1percent, zirconium up to 0.5 percent, cobalt up to 1 percent andmixtures thereof, and the balance essentially copper.
 7. In a glass orceramic-to-metal seal as in claim 6, the further improvement wherein thecopper base alloy consists essentially of 2.5 to 3.1 percent aluminum,1.5 to 2.1 percent silicon, 0.25 to 0.55 percent cobalt and the balanceessentially copper.
 8. In a glass or ceramic-to-metal seal as in claim7, the further improvement wherein a semi-conductor device is secured tothe base portion of said metal header and a metal cap is placed oversaid metal header so as to enclose the semi-conductor.
 9. In a glass orceramic-to-metal seal as in claim 8, the further improvement whereinresidual stresses in said glass or ceramic are compressive in nature andwherein the mismatch in coefficient of thermal expansion between theglass or ceramic and the copper base alloy is less than 110 X 10 7in./in./*C.